\documentclass{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}\frac2\pi=
\frac{\sqrt2}2
\frac{\sqrt{2+\sqrt2}}2
\frac{\sqrt{2+\sqrt{2+\sqrt2}}}2\ldots\end{equation*}
\end{document}
